"The Baltic Dry Index (BDI) is a number (in USD) issued daily.
...the index provides "an assessment of the price of moving the major raw materials by sea.
Taking in 23 shipping routes measured on a timecharter basis, the index covers Handysize, Supramax, Panamax, and Capesize dry bulk carriers carrying a range of commodities including coal, iron ore and grain.
Most directly, the index measures the demand for shipping capacity versus the supply of dry bulk carriers. The demand for shipping varies with the amount of cargo that is being traded or moved in various markets (supply and demand).
Because dry bulk primarily consists of materials that function as raw material inputs to the production of intermediate or finished goods, such as concrete, electricity, steel, and food; the index is also seen as an efficient economic indicator of future economic growth and production.
The BDI is termed a leading economic indicator because it predicts future economic activity."